Method of operating regenerative furnaces



May 29, 19281 A. N. DIEHL ET AL.

'METHOD O F OPERATING REGENERAT-IVEFURNACES lFiled July 9. 1921 2 Sheets-Sheet4 2 MMA m, N d

l'fmsses.

PafeniedMay 29, 192,8.

PATENT ori-Ica Mimosa N. DIEHI. AND SAMUEL e. Won'rornorf DUQUESNIENNSYLVANIL.

i METHOD F OPERATING REGENERATIVE FURNACES.

Application filed July 9, `1921.

This invention relates to the operation of 'regenerative furnaces and, while not re stricted thereto, more particularly relates'to the operation of regenerative open hearth furnaces lused in the manufacture of steel and similar reducing and refining operations.

i One object of vour invention is the provision of a novel method of burning the gaseous fuel used in heating such regenerative furnaces, wherein light gases 4such as by-product coke oven gases may be eml ployed without the aid or addition of tar or oil or other illuminants, and wherebyl complete combustion of the gases is obtained, the use of an excess of air is avoided yinburning the gases, andthe life of the Vroofs of-such furnaces is materially lengthened.

Anotherobject of our invention is to provide a novel method of burning light gases, such as debenzolized Iby-product 'coke oven gases, wherein the usual lack of luminosity in the .flame of the burning gases is overcome, the gases are vburnedwith a luminous flame, and whereby luminosity of the flame is regulated. and controlled and, when desired, is prevented. y

The above and various other objects and advantages will be more fully brought` out in the followingspecification and will be illustrated in the accompanying drawings., in'which* Figure 1 'is a sectional plan of an open hearth furnace adapted forense in carrying out our invention.

Figure 2 isr a sectional elevation of the same, the section being ltaken on the line II-II of Figure 1.

Figure 3 isa plan showing on an enlarged scale, a` preferred form of auxiliary gas burner by which a mixture of gas and air may be supplied to the furnace.

Referring now particularly to the drawings forming part ofthislspeciiicat-ion, the.

numeral 2 designates the hearth of a regenerativeopen. hearth furnace which is of the usualdesign. The furnace is provided with a central gas port 3 and two air ports 4 and v5 at each ofthe opposite endsof the fur-A nace hearth. The ports are arranged in the same manner at each end of the hearth soit is to be lunderstood that the description of one will apply to both ends.,

The furnace shown by the drawings as Serial N0. 483,500.

originally built was adapted for burning producer gas, and, therefore, the gas port 3 1s connected at its rear end with a vertical flue (3 leading upwardly from a slag pocket 7, and the slag pocket is connected by a port 8 with a regenerator chamber 9, which in turn is connected by a flue 10 with a double valve casing 11 having a stack valve 12 and a gas valve 13 therein, the valve casing 11 being adapted to connect the flue 10 with either the stack flue 14 or producer gas flue 15, according to which of the valves 12 and 13 is raised into open position.

The valve casing 11 has manholes 16 which normally. are open only to permit'of inspection, for repairs, etc. of the valves 12 and 13, and interior of the valve casing, and which remain 'closed at other times. A new use is made `of these manholes in 'connection with our invention, which will be more fully brought out later.` i

The gas flue 15 through which the gas is supplied to the furnace when burning producer gas is provided with a sand damper 17 for sealing the flue 15 when the furnace is operated withbyfproduct coke oven gas; this damper remaining in sealing position at all times when operating the furnace in accor-dance with this invention.

The air ports 4 and 5 are connected by lues 18 and 19 with a slag pocket 7a running parallel with the slag pocket 7 for the gas port, and the slag pocket 7 is connected at one end by the horizontal flue 2() with an air regenerator chamber 21, which in turn is connected by a horizontal flue 22 with the stack flue 23 leading to the Stack 2A. Each of the flues '22 is provided adjacent the end thereof communicating with ythe stack flue 23, with a sliding shutter or damper valve 25, so that one of theA fines 22 may be cut off `from the` stack 24 when the end of the furnace with which such flue 22 `connects isbeing used to supply fuel to t-hey furnace hearth. It will, of course, be

understood vthat the furnace being of the reversing type, at such time the other flues v22 and 10 will be used to conduct the products of combustion passing throu h the air furnace, the valve 26 being open when the damper valve 25 is'closed.

In adapting the above described furnace vto carry out the method to be described, the

'oppositely directed streams of gas across the Width and also lengthwise Aof the gas port 3 and at right angles to the stream of air flowing to the furnace hearth through .the

port 3, and supplied thereto by the vertical flue 6, as referred to later. y

I The end inlets as shown. comprise a tube 33 projecting through the furnace end wall into the port 3. The rear end of the burner tube 33 is telescoped over a gas supply tube 34 of less diameter, this smaller tube 34 hav ing a nozzle or contracted outlet-35. The

tube 33 also is provided at its rear end with an air inlet opening 36, a slidable gate or shutter 37 being pivotally connected thereto so as to provide means for regulating and controlling the amount of air drawn ,into the tube by the aspiratingveifect of the gas discharged from the nozzle 35. The gas supply pipe 29*aL is connected to the same Y gas supply main as the pipes 28 and 29, and a valve is v'provided'on the pipe 29a as Well as on the pipes 28 and 29 to control, andY shut otl' the gas supply.

The manholes 16 1n the valve casings 11 have their usual covers removed, and a hinged cover plate 32 is substituted therefor.`

'The cover plate 32, which must be`.1aised and lowered in connection with our improved method, is connected by a chain or. other flexible connection 32 to a cross bar 34 secured to the gas valve 13, so` that by raising the gas valve 13 with its usual operating mechanism the cover 32 vwill be lifted to open the manholes to the atmosphere and permit inflow of air. y

By properly adjusting the amount of lifting movement of the cover plates 32,

(through the medium of the chains 32) it is made possible for the luminosity of the flame in the furnace hearth to be regulated and controlled and prevented at will7` by manipulation of the gate or shutter 3 on the air inlet 36 of the combined gas and air inlet tube 33.

In the usual operation of the furnace when using producer gas, the gas valves 13 are lifted or opened when supplying gas to the incoming end of the furnace, and the same lifting operation is maintained in utilizing' the present method, except that the gas valve itself has no function other than as a medium to operate the cover plate 32,V

since the producer gas main is sealed by the :sand damper 17. Raising of the cover plate 32 will allow air to be; drawn by suction through the manholes 16 into the flue 10, re- V generator chamber 9, vertical flue 6, and into the gas port 3 where it mixes with the gases Supplied to the combustion chamber through ,the gas supply pipes 30, 31, and 33.

Our improved method of heating the furnace with by-product coke oven gases Will now be set out in detail, it being expressly understood that the method is not limited to a furnace constructed in the precise manner set forth above,since different forms of furnaces and various arrangements of the ports may be devised for carrying out the method.

By product coke oven gases either washed.

, or unwashed, are supplled tothe furnace from a suitable main through the pipes 30, 31, and 33, which deliver the gases to the gas port 3. At the rsame time the cover plate 32 on the manhole 16 communicating with the flue 10 on the incoming end of the furnace allows air, in amounts insufiicient to completely burn the gases .to be drawn into the flue 10, and through the regenerator 9 (the regenerator ordinarily used to preheat producer gas) to the gas port 3. The air, which becomes heated in its passage through the regenerator, mixes with the gas entering the port 3, where ignition instantly begins. By adjusting the shutter 37' on the suppl pipe 33 additional amounts of air may e obtained. The maximum luminosity ofv the flame is obtained when a mixture of air and gases having approximately-50 per cent of the theoretical volume of air required for complete combustion is drawn into the port 3 and becomes mixed with the-.gases supplied by the pipes 30, 31, and 33, the burning mixture passing to the nose .of the port where the additional air needed for complete combustion is supplied, combustion of the gases being completed before the ports at the opposite or outgoing side of the furnace is reached. The amount of air entering the port 3 may be varied by adjustin the cover plate 32 or the gate or shutter 3 and in this manner means are provided whereby more or less luminosity may be obtained by increasing or decreasing the volume of air supplied to the port 3.

The mixture of air and gases is ignited in passing through the port 3, and combustion is partially completed by the time the burning mixture reaches the nose of the port and emerges into the furnace hearth 2. The temperature of the partly burned mixture within the port 3 is sufficiently high to partially decompose, Within the port 3, the hydro-carbons present inthe mixture and results in the splitting up of the same, with a resultant partial dissociationv of the, carbon and hydrogen. 'Air in amountsl suilicient to complete combustionA of the mixture is musas i drawn through the air valve 26 in the Hue controlled so that dissociation takes place' 252, and after .being heatedin the air regenerator, passes through the airports 4 and 5 into the hearth 2, where it mixes with the .partially burned gases issuing from the gas port 3. A secondary or complete combus` tion then takes place across the furnace hearth which is completed by the time'the gases reach `the gas port 3 and air ports 4 and 5 on the outgoing end ofthe furnace, through which the products of combustion pass from the furnace.

Heretofore by-product lcoke oven gases -on account ofthe large hydrogen content described above to produce a luminous Haine lWith by-product gases and to control the degree of luminosity, the difficulties in judging thel fiame temperatures are avoided and overcome. As the degree of combustion is `Within the gas port 3 and later complete combustion-occurs in the hearth, with a properly designed burner nozzle and port the gases can'. be directed upon the charge on the hearth of the furnace and away from the furnace roof so that the roof difficulties heretofore encountered are eliminated.

As has been said before, the luminosity ofl the flame will vary with the amount of air introduced into the gases prior to .the complete combustion thereof, so that when the amount of air introduced or mixed with the gases in the port 3 is insufficient to completely burn the gases and vthe'so-called mixture is only` partly consumed While in the port, and 1s afterward completely con.- sumed within the furnace, the resulting flame will be luminous. As the amount of air mixed with thegases in the port 3 is increased so will the luminosity of the resulting flame be vproportionally lessened until when the amount of a'ir entering thel port- 3 with the gases is sufficient to completely burn the gases, the resulting flame Will be practically non-luminous. In other words when air is supplied to the port 3 with the gases prior to the entrancev of the mixture to the furnace hearth, the luminosity of the flame in the hearth will be increased in inverse proportion `to the amount of air supplied to the port.`

The many advantages of operating regenerative furnaces in accordance with our improved method Will be apparent to those skilled in the art. By partly consuming the gases before they emergeinto the furnace hearth, by-product coke oven gases can I be broken'up so as to provide a luminous flame and by regulating the amount of air supplied to the gases in the gas port, the

lluminosity of the flamer may be accurately controlled. Through the luminosityof the fiame it is possible to accurately gauge the furnace temperatures, While a properly designed port directs the gases intov the 'hearth so as to lengthen the life of the roof with the consequent increasedperiod of production of the furnace.

Various modifications of the above method.

and the apparatusvused in carrying out the method may be made without departing from the spiritof the invention as defined inv the appended claim; for example, the air may be preheated or not, without materially' affecting the operation ofthe invention, or

'the combustible gases may be other than,

by-product coke oven gases andv the number and type of gas supply pipes may be varied.

In. the operation ofL regenerative` furnaces, the method of firingv furnaces with by-product c oke oven gas without the addition of illuminants, which consists in breaking up the hydrocarbons contained in the gas to be fired by mixing with the gas approximately fifty per cent of the amount of preheated air necessary to support com,-

plete combustion and causing partial combustion of the mixture, thenpassing a stream of the mixture after partial combustion into :si

the furnace, andsupplying additional pretities suflicient to support complete combustion of the mixture Within the furnace.

In testimony whereof We have hereuntol A heated air to the furnace, hearth 1n quan- 

